Monday, January 9, 2012

TRADITIONAL METHODS OF RAINWATER HARVESTING

Water has been harvested in India since antiquity, with our ancestors perfecting the art of water management. Many water harvesting structures and water conveyance systems specific to eco-regions and culture has been developed. There are evidences that, even during Harappan period, there was very good system of water management as could be seen in the latest excavation at Dholavira in Kachch.

Traditional rainwater harvesting which is still prevalent in rural areas was done in surface storage bodies like lakes, ponds, irrigation tanks, temple tanks etc. In urban areas, due to shrinking of open spaces, railways will have to necessarily be harvested as ground water, hence harvesting in such places will depend very much on the nature of soil viz., clayey, sandy etc.

According to Londonkar (2007) various kinds of traditional rainwater harvesting can be described as follows:

SPaar System

Paar is a common water harvesting practice in the western Rajasthan region. It is a common place where the rainwater flows from the agar (catchments) and in the process percolates into the sandy soil. In order to access the rajani pani (percolated water) kuis or beris are dug in the agar (storage area). Kuis or Beris are normally 5 mts to 12 mts deep. The structure was constructed through traditional masonary technology.

This is the most predominant form of rainwater harvesting in the region. This method is also known as Patali Paani.

STalab / Bandhis

Talabs are reservoirs. They may be natural, such as the ponds (pokhariyan) at tikamgarh in the bundelkhand region. They can be human made. A reservoir area of less than five bighas is called a talai, a medium sized lake is called a Bandhi or Talab, and bigger lakes are called sagar or samand. The pokhariyan serve irrigation and drinking purposes.

SSaza Kuva

An open well with multiple owners (Saza= partner),Saza Kuvais the most important source of irrigation in the Aravalli hills in Mewar, eastern Rajasthan. The soil dug out to make the well pit is used to construct a huge circular foundation or an elevated platform sloping away from the well.

Saza Kuvaconstruction is generally taken up by a group of farmers with adjacent landholdings.

SJohad

Johadsare small earthen check dams that capture and conserve rainwater, improving percolation and groundwater recharge. Starting 1984, the last sixteen years have seen the revival of some 3000Johadsspread across more than 650 villages in Alwar district, Rajasthan. This has resulted in a general rise of the groundwater level by almost 6 metres and a 33 percent increase in the forest cover in the area.

Five rivers that used to go dry immediately following the monsoon have now become perennial, such as the River Arvari, has come alive.

SPat System

This system was devised according to the peculiarities of the terrain to divert water from swift-flowing hill streams into irrigation channels called pats. The diversion bunds across the stream are made by piling up stones and then lining them with teak leaves and mud to make them leak proof. The pat channel has to negotiate small nullahs that join the stream off and on and also sheer cliffs before reaching the fields.

The villagers irrigate their fields by turns. The channel requires constant maintenance and it is the duty of the family irrigating the fields on a particular day to take care of the pat on that particular day.

SNaada / Bandha

Naada/Bandhais found in the Mewar region of the Thar Desert. It is a stone check dam, constructed across a stream or gully, to capture monsoon runoff on a stretch of land. Submerged in water, the land becomes fertile as silt deposits on it and the soil retains substantial amounts of water.

SRapat

A Rapat is a percolation tank, with a bund to impound rainwater flowing through a watershed and a waste weir to dispose of the surplus flow. If the height of the structure is small, the bund may be built of masonary, otherwise earth is used.Rapats and percolation tanks do not directly irrigate land, but recharges well within a distance of 3-5 km downstream.

SChandela tank

These tanks were constructed by stopping the flow of water in rivulets flowing between hills by erecting massive earthen embankments, having width of 60m or more. These hills with long stretches of quartz reefs running underneath them, acted as natural ground water barrier helping to trap water between the ridges. The earthen embankments were supported on both sides with walls of coarse stones, forming a series of stone steps. These tanks are made up of lime and mortar and this is the reason why these tanks survived even after thousand years but the only problem, which these tanks are facing, is siltation of tank beds.

SBundela Tank

These tanks are bigger in size as compared to Chandela tanks. These tanks had solidly constructed steps leading to water in the tank but these structures had chabootaras, pavillions and royal orchards designed to show off the glory of the king who built them. But these tanks are not as cost effective and simple as Chandela tanks. These tanks were constructed to meet the growing water demands in the area; maintenance of these tanks was done by the person employed by the king but in case of smaller tanks villagers collectively removed silt and repair embankment.

SKunds / Kundis

Akundorkundilooks like an upturned cup nestling in a saucer. These structures harvest rainwater for drinking, and dot the sandier tracts of the Thar Desert in western Rajasthan and some areas in Gujarat. Essentially a circular underground well,kundshave a saucer-shaped catchment area that gently slopes towards the centre where the well is situated. A wire mesh across water-inlets prevents debris from falling into the well-pit. The sides of the well-pit are covered with (disinfectant) lime and ash. Most pits have a dome-shaped cover, or at least a lid, to protect the water.

They can be owned by only those with money to invest and land to construct it. Thus for the poor, large publicKundshave to be built.

SBaoris / Bers

Baorisorbersare community wells, found in Rajasthan, that are used mainly for drinking. Most of them are very old and were built bybanjaras(mobile trading communities) for their drinking water needs. They can hold water for a long time because of almost negligible water evaporation.

SJhalaras

Jhalaraswere human-made tanks, found in Rajasthan and Gujarat, essentially meant for community use and for religious rites. Often rectangular in design,Jhalarashave steps on three or four sides.Jhalars are ground water bodies which are built to ensure easy & regular supply of water to the surrounding areas.The water from these Jhalaras was not used for drinking but for only community bathing and religious rites. Jodhpur city has eight Jhalaras two of which are inside the town & six are found outside the city.

SNadis

Nadisare village ponds, found near Jodhpur in Rajasthan. They are used for storing water from an adjoining natural catchment during the rainy season. The site was selected by the villagers based on an available natural catchments and its water yield potential. Water availability from nadi would range from two months to a year after the rains.

STobas

Tobasis the local name given to a ground depression with a natural catchment area. A hard plot of land with low porosity, consisting of a depression and a natural catchment area was selected for the construction of Tobas.

STankas

Tankas(small tank) are underground tanks, found traditionally in most Bikaner houses. They are built in the main house or in the courtyard. They were circular holes made in the ground, lined with fine polished lime, in which rainwater was collected.The water was used only for drinking. If in any year there was less than normal rainfall and theTankasdid not get filled, water from nearby wells and tanks would be obtained to fill the householdTankas.

Thetankasystem is also to be found in the pilgrim town of Dwarka where it has been in existence for centuries. It continues to be used in residential areas, temples,dharamshalasand hotels.

SKhadin

Akhadin, also called as adhora, is an ingenious construction designed to harvest surface runoff water for agriculture. Its main feature is a very long (100-300 m) earthen embankment built across the lower hill slopes lying below gravelly uplands. Sluices and spillways allow excess water to drain off. Thekhadinsystem is based on the principle of harvesting rainwater on farmland and subsequent use of this water-saturated land for crop production.

A similar system is also reported to have been practiced 4,000 years ago in the Negev desert, and in southwestern Colorado 500 years ago.

SVav / vavdi / Baoli / Bavadi

Traditional step wells are calledVavorvavadiin Gujarat, orbaolisorbavadisin Rajasthan and northern India. Built by the nobility usually for strategic and/or philanthropical reasons, they were secular structures from which everyone could draw water. Most of them are defunct today. Step well locations often suggested the way in which they would be used. When a step well was located within or at the edge of a village, it was mainly used for utilitarian purposes and as a cool place for social gatherings. When step wells were located outside the village, on trade routes, they were often frequented as resting places. Many important step wells are located on the major military and trade routes from Patan in the north to the sea coast of Saurashtra.

SAhar Pynes

Anaharis a catchment basin embanked on three sides, the 'fourth' side being the natural gradient of the land itself. Ahar beds were also used to grow arabi(winter) crop after draining out the excess water that remained afterkharif(summer) cultivation.Pynesare artificial channels constructed to utilize river water in agricultural fields. Starting out from the river,pynesmeander through fields to end up in an ahar. Most pynesflow within 10 km of a river and their length is not more than 20 km.

SBengal's Inundation Channel

Bengal once had an extraordinary system of inundation canals. Sir William Willcocks, a British irrigation expert who had also worked in Egypt and Iraq, claimed that inundation canals were in vogue in the region till about two centuries ago.

According to Willcocks, the distinguishing features of the irrigation system were:

üThe canals were broad and shallow, carrying the crest waters of the river floods, rich in fine clay and free from coarse sand.

üThe canals were long and continuous and fairly parallel to each other and at the right distance from each other for purposes of irrigation.

üIrrigation was performed by cuts in the banks of the canals, which were closed when the flood was over.

SDungs or Jampois

Dungs or Jampois are small irrigation channels linking rice fields to streams in the Jalpaiguri district of West Bengal.

SKohli Tanks

The Kohlis, a small group of cultivators, built some 43,381 water tanks in the district of Bhandara, Maharashtra, some 250-300 years ago. These tanks constituted the backbone of irrigation in the area until the government took them over in the 1950s. It is still crucial for sugar and rice irrigation. The tanks were of all sizes, often with provisions to bring water literally to the doorstep of villagers.

SKul

Kulsare water channels found in precipitous mountain areas. These channels carry water from glaciers to villages in the Spiti valley of Himachal Pradesh. Where the terrain is muddy, thekulis lined with rocks to keep it from becoming clogged. In the Jammu region too, similar irrigation systems calledkuhlsare found.

SNaula

Naula is a surface-water harvesting method typical to the hill areas of Uttaranchal. These are small wells or ponds in which water is collected by making a stone wall across a stream.

SZings

Zingsare water harvesting structures found in Ladakh. They are small tanks, in which collects melted glacier water.Essential to the system is the network of guiding channels that brings the water from the glacier to the tank. As glaciers melt during the day, the channels fill up with a trickle that in the afternoon turns into flowing water. The water collects towards the evening, and is used the next day.

A water official called thechurpunensures that water is equitably distributed.

SKere

Tanks, called Kere in Kannada, were the predominant traditional method of irrigation in the Central Karnataka Plateau, and were fed either by channels branching off fromanicuts(chech dams) built across streams, or by streams in valleys. The outflow of one tank supplied the next all the way down the course of the stream; the tanks were built in a series, usually situated a few kilometers apart.

This ensured:

a) No wastage through overflow.

b) The seepage of a tank higher up in the series would be collected in the next lower one.

2 comments:

Thanks for providing such a wonderful techniques for harvesting rain water,and i think rooftop rainwater harvesting is also best water harvesting system Because the rooftop serves as the catchment area, the amount and quality of rain water depends upon the standard of the covering substance and its complete region.